In a known manner, rotary electrical machines comprise a stator and a rotor integral with a shaft. The rotor can be integral with a driving and/or a driven shaft, and can belong to a rotary electrical machine in the form of an alternator, as described in document EP0803962, or of an electric motor as described in document EP0831580. The electrical machine comprises a housing which supports the stator. This housing is configured to rotate the shaft of the rotor, for example by means of bearings.
The rotor comprises a body formed by a stack of metal sheets which are maintained in the form of a set by means of an appropriate securing system, such as rivets which pass through the rotor axially from one side to the other. The rotor comprises poles which are formed for example by permanent magnets accommodated in cavities provided in the magnetic mass of the rotor, as described for example in document EP0803962. Alternatively, in a so-called “projecting” poles architecture, the poles are formed by coils wound around arms of the rotor.
The stator comprises a body constituted by a stack of thin plates, as well as a phase winding received in notches in the stator which are open towards the interior. There are generally three or six phases. In the stators of alternators of this type, the types of windings which are most commonly used are firstly the so-called “concentric” windings constituted by coils closed on themselves, which are wound around teeth of the stator, and secondly windings of the so-called “undulating” type, which are described for example in document FR2483702.
The undulating winding comprises a plurality of phase windings, of the type wherein each winding comprises at least one spiral conductor, each spiral of which forms undulations which pass through the notches in the body. These conductors have loop structures which are situated alternately on both sides of the rotor or the stator, connecting to one another segment structures which are situated in the interior of the notches in the stator. A set of loop structures which extends from a side of the stator constitutes a chignon of the winding.
In order to improve the performance of the electrical machine, it is preferable to fill the notches in the stator to the maximum, whilst facilitating the formation of the winding chignons. For this purpose, for stators constituting alternators which are designed in particular for motor vehicle applications, it has been proposed in document U.S. Pat. No. 6,459,187 to produce windings of the so-called “front-rear” type, comprising phase windings formed by conductors with segment structures which are positioned alternately in an inner radial layer and an outer radial layer of the conductor.